# BAD
from typing import Optional


def foo(li: list = []):
    li.append(1)
    print(li)


# GOOD
def foo2(li: Optional[list] = None):
    li = li or []
    li.append(1)
    print(li)


foo([])
foo([])
foo([])
foo()
foo()
print('===========')
foo2()
foo2()
foo2()
